1. Field of the Invention:
Underwater breathing apparatus of the closed-loop type wherein a pump system at a diving bell or chamber effects circulation of breathing gas to and from a diver via flexible hoses.
2. Description of the Prior Art:
Insofar as applicants are aware, usual prior art breathing apparatuses of the push-pull closed-loop type having pumping systems circulating breathing gas between diving bell and diver via flexible hoses, umbilicals, commonly operate at constant supply and return pressures at magnitudes sufficient to force the flow of breathing gas to the diver at his deepest depth and to induce return flow of the breathing gas from the diver to the bell at the diver's shallowest depth, while at the same time overcoming the dynamic pressure losses in the bell-to-diver circulatory system. This requires greater than a desired amount of pump-operating power, it tends to create a high noise level, and it requires supply and return hose sizes commensurate with such relatively high pressure and flow operating parameters.